Telescopic suspension device for vehicles



m, Filed Sept. 21, 1944 July`12, 1Y 949. P. w. THoRNHlLL 2,476,228

TELESCOPIC SUSPENSION DEVICE FOR VEHICLES Patented July 12, 1949 UNITEDSTATES PATENT OFFICE TELESCPIC SUSPENSIN- DEVICE FOR VEHICLES' PeterWarborn Thornhill, Leamingtonspa, England, assignertofLevitationLimitedf This invention relates to telescopic suspensiondevices for vehicles and especially to those in which the telescopicmovement of the elements is damped by a uid medium, such, for instance,as compressed gas, or liquid.

It is the object oi the invention to provide an improved telescopicsuspension device incorporating a simple but eicient means for checkingthe rebound or extension stroke. The invention is of particular utilityin connection with the suspension device described in my applicationSerial No. 555,150, led September 21, 1944, (corresponding to BritishPatent Application No. 14375/43), where compressed air or other gas isused as the resilient medium and also as thev means for damping thetelescopic movementsv ofr the elements. The improved means may, however,be used in connection with oleo-pneumatic suspension devices Wherecompressed gas Constitutes the resilient medium for sustaining. the loadand liquid is used for damping telescopic movements of the elements.

In a telescopic suspension device for a vehicle, according to theinvention a chamber, which decreases in volume as the device lengthens,has the escape of fluid from said chamber controlled by valve means,which latter is normally open butr 1s caused to close as the suspensiondevice eX- ceeds a predetermined length, thus trapping gas within saidchamber so that further lengthens ing movement causes the pressure ofsaid gas to be progressively raised, thereby creating substantialresistance opposing said lengthening movement.

The invention is illustrated by way of example in the accompanyingdiagrammatic drawings, in which:

Figure 1 is an elevation, partly in section, showing a typicaltelescopic suspension unitincorporating the improved snubbing means;

Figure 2 is a fragmentary sectional elevation, drawn to an enlargedscale and showing the snubbing means in action;

Figure 3 is a fragmentary sectional elevation showing a modiiiedconstruction of snubbing cap II. having an attachment lug I2. At its10W- er end the cylinder I0 is provided with an internal packing I3,which engages in a fluid-tight manner*- With theoutside ofthe rod-likestem member ifiy of a plunger indicatedl generally at I5. This plungerI5 also has at its upper end a piston head iii, which is just slightly.vsmaller in diameter than the'bore il of the cylinder I0 and is iittedwith a. circumferential packingl I8 providing a fluidtight sealbetweenthe outside` of the piston head 5 and the bore I-T. The piston head I6is tted with a damping valve'- device, which is indicated generally atI9` and-can be of any form, such, for instance, as that described in theabove-mentionedf application; It forms a means ofcomchargedwit-hcompressedr air or other gas through an inletl valve 23;the air or other gas acts as a resilient medium tending to extend thesuspension unit wth'suiicient force to support the load Y on the device.30

Upon reference to'Figure 7 it can be seen that the damping valve deviceis comprised of a hollow piston valve 60' which' makes a sliding t in anappropriate socketV 6I located in the upper end ofthe plunger I5. Theupper face of the piston valve 6B is provided with an axial bore that isthreaded to receive a bush y62 having a constricted' passage' 63`communicating at all times with space 2li. Attached to and depending'from bush (i2, is atube 64. The side of the piston valve GEI isprovided' with an annular groove 5,5. which,A depending upon thevertical position. ofthe piston valve tu relative to the ilunger I5,establishes communication between the portsA 2|' and'ports 66 thatextend. out radial- 1y above theV packing I8` in communication with thespace 2G. The construction. of Figurev 7 constitutes no part of thepresent inventiony and is fully described in application, No. 555,150filed September 21, 1944.

1n operation lthe damping valve controls the rate ofy transfer of;iluids to and from the spaces 2li andl 22.

The lower part' ofthe stem Id is'provided with. a lug 2liy forattachmenttothe wheel axle or equivalent'. a' tubular iiexibl'e boot 25being provided to exclude dirt and other foreign matter from the outersliding surface of the stem I4. When the vehicle is standing, or isrunning along a smooth road, the piston head I6 occupies approximatelythe position shown in Figure l, the pressure exerted by the compressedair or gas downwards upon the piston head I6 over an area correspondingto the cross-sectional area of the stem I4 serving to support thegravitational load on the suspension device. When the vehicle istravelling and the Wheel strikes a bump the plunger I5 rises within thecylinder Ill, thus re-V ducing the volume of the cylinder working space29 and causing part of its air content to be transferred through thedamping valve device I9 and passages 2I to the annular working space 22;the total volume of the spaces 20 and 22 is, however, less than before,and therefore the pressure of the air is increased to an extentdepending upon the amount of shortening of the device. As a result ofthis the shortening stroke is followed by a lengthening or recoilstroke, the speed of which is usually governed by the damping valvedevice IS, which latter acts to restrict the return flow of air from theworking space 22 back into the cylinder space 2li.

It is found that when an exceptionally strong shock is received by thesuspension device the maximum restraint which is offered by the dampingvalve I9 is insufficient to resist the following recoil stroke, andtherefore there is danger of the suspension device becoming extended toits maximum length, with consequent noise and possibly damage to thesuspension. With a view to avoiding this the improved suspension deviceincorporates snubbing means which come into action when the operativelength of the suspension device exceeds a predetermined value, whichvalue, of course, is greater than the normal length when the suspensiondevice is bearing its static load. The snubbing means also becomeoperative during an initial lengthening stroke, such as when the wheelsdrop down a curb.

The snubbing device shown in Figures 1 and 2 comprises a ring 26, whichis of somewhat triangular cross-section and is disposed within theworking space 22. It is composed of relatively flexible material, such,for instance, as rubber or rubberised canvas, and it has an inwardlyfacing frusto-conical surface 2l, the internal margin of which is asmooth sliding nt upon the stem I4; the outside diameter of the ring 26is substantially smaller than the cylinder bore I'i so as normally toallow the free flow of air past the outside of the ring 26. That part ofthe piston head I6 below the passages 2I is shaped toprovide afrusto-conical annular surface 23 adapted to engage with thecorresponding surface 21 of the ring 26. Also disposed within theworking space 22 is a relatively strong coiled. compression spring 29,the lower end of which bears against an abutment ring 30, which latteris supported by a tubular spacing member 3i. A metal washer 32, smallerin radial width than the working space 22, is interposed between theupper end of the spring 29 and the flat under surface of the ring 26.

As the recoil extension stroke of the suspension device proceeds and theabove-mentioned predetermined length is exceeded, the frustoconicalsurface 28 of the piston head I comes into engagement with the iiexiblering 23, and owing to the resistance afforded by the spring 29 the upperpart of said ring 216 is caused by the surface 23 to stretch until thering 2S engages thecylinder bore I1 in a substantially duid-tightmanner, as will be seen more clearly in Figure 2. This seals the workingspace 22, so that the air or other gas which is trapped therein isprogressively compressed so long as the recoil stroke continues, thusaffording a substantial and increasing resistance to further lengtheningof the suspension device. In addition, of course, the spring 29 becomescompressed by the recoil movement, and this also acts to arrest therecoil movement of the plunger I5.

A somewhat similar construction of snubbing device is shown in Figure 3,and in this case the lower part of the cylinder I0 is slightly enlargedin diameter at Illa so as to form a shoulder 33. A ring 34 composed ofmetal `or other relatively rigid material is slidably mounted within thebore 35 of the enlarged portion Ia, a fluid-tight seal between theoutside of the ring 34 and said surface 35 being secured owing to theprovision of a packing ring 36. The ring 34 has at its upper part aninwardly facing frusto-conical surface 21a, which is adapted to beengaged in a substantially :fluid-tight manner by the frusto-conicalsurface 28 of the piston head IE. The ring 3l! is normally held inengagement with the shoulder 33 by the coiled compression spring 29.When the suspension device becomes lengthened beyond a predeterminedamount, as, for instance, during a violent recoil stroke, thefrusto-conical surface 28 seats upon the ring 34 and consequently formsa seal, which traps the compressed air or other gas Within the annularworking space 22, so that further lengthening of the device causes thering 34 to slide within the enlarged portion 10a of the cylinder andthus rapidly bring the air or other gas within the space 22 to a veryhigh state of compression. During this movement the spring 29 is alsocompressed and thus tends to prevent further extension of the device.

It will be seen that in the arrangement shown in Figures 1 and 2 thering 26, acting in conjunction with the piston head I6, constitutes avalve device which closes when the suspension device exceeds apredetermined length, while in Figure 3 the ring 34 co-operates with thepiston head Iii to produce a similar effect. Some modified forms ofvalve device are shown in Figures 4 to 6, but in each case the effect isthe same, namely to close and seal the annular working space 22 after apredetermined extension of the device has occurred.

In the arrangement shown in Figure 4 an endless circumferential lip 31is formed upon the piston head I6 just below the passages 2| from thedamping valve I9, said lip being adapted to engage in a fluid-tightmanner by a, ring 38. This ring, which is conveniently composed ofrubber or rubberised canvas, slides snugly within the cylinder bore I'Iso as to have a substantially huid-tight t therein. As before, a coiledcompression spring 29 is provided and rests at its lower end upon a ring39, which latter is supported by an internal shoulder 40 pressed intothe cylinder tube III; a washer 4I is interposed between the upper endof the spring 29 and the ring 38. The stem portion I4 of the plunger istubular for convenience in construction, and where its upper end isfitted to the piston head I5 it is arranged to hold in position anannular stamping 42, which is composed of springy material and has aplurality of downwardly inclined tongues or lingers 43, which extendoutwards nearly as far as the lip 31. As the piston head amazes.

I-B 'moves #downwards during lengthening of. the

lip 3l, the tongues i3 being deected upwards. Therefore a fluid-tightseal -is produced. between the ring 38 andthe lip 3l, thus closingtheannular working space 22. During the succeeding snortening stroke, asthe spring 29 resumes its naturallength, the ktongues d3 lightly pressthe ring 38 away from the lip 3'?, thus breaking the seal and enablingthe piston'head I5 to leave the ring 338 behind.

In the construction shown in Figure the piston head i6 is formed, belowthe packing ring t8, witha depending flange 'lill dening an annularspace 5 into which lead the passages 2l of the damping valve IS. Anannular valve member d6 1s secured to the piston head l' by means of thestem tube lll, and is composed of springy material shapedso as to assumea position in which its outer margin is spaced from the lower edgeof theflange lill, as shown in Figure 5. A coiled compression spring 29 isprovided as before, and serves tol support a washer ll slidable in thecylinder. i0. As the piston head I6 slides down the cylmder tube lllduring lengthening of the suspens1on device the annular valve member itcomes mto contact with the washer li and is deflected thereby so as tomake a substantially fluid-tight seal against the lower edge of theflange M. This, of course, seals the annular working space 422 from thedamping valve i9 and rapidly arrests the extending movement 'of `thedevice owing to the compression which takes place in the air within thespace 22 and also in the spring 29.

Another form of valve device is shown in Figure 6, and in this case asleeve il is slidably mounted upon the outside of the plunger stern i4,a sealing ring i3 being provided in order to prejvent leakage betweenthe sleeve l? and said plunger stem. A -eoiled compression spring 49bears at its upper end against the piston head it. While its lower endengages a shoulden upon the sleeve el, said spring normally causing thesleeve l1 to be depressed so that its upper edge lies below the passages2i leadmg to the damping valve I9. A coiled compress1on sprmg 29 is ttedwithin the lower part of the cylinder tube ID and is tted with a washer4I, so that when the device extends beyond a predetermined length thelower end of the sleeve d? engages with the washer 4l. Continuedmovement causes the spring 29 to be compressed and the piston head l5passes downwards through the sleeve 41 un t1l the latter completelycloses the passages 2 l. Th1s, of course, isolates the annular workingspace 22 so that further lengthening of the suspension device createssubstantial increase in pressure 1n the air which is trapped Within thespace 22.

In suspension devices of the pneumatic type as described, it is usuallydesirable to insert a quantity of lubricating liquid, such as oil, toprevent wear of the parts and also to render the packing i3 as efficientand frictionless as possible. As there is some risk of this liquidaccumulating within the annular working space 22, it may be desirable insome cases to provide an auxiliary space within which the air or othergas can be compressed when the snubbing device is in action. Thus in theconstruction shown in Figure 2, the stem I4 is tubular, and the pistonhead i6 is formed at its lower part with a wide circumferential groove5I, thus producing an annular auxiliary space 52 which is in permanentcommunication at its upper part with the working space 22 6 through oneor -nidre'holes inth'e -stem-- 14; auxiliary space of this nature can,4of course, be

readily `provided-"in 'conjunction with any of tneconstructionsillustrated'.

It will be 'understood that various other 'modifi'icaticns may 'be made,andl ythat the invention is applicable `-to various vforms of telescopicsus- Ipension device, such, for instance, as those which employ liquidas a 'damping medi-um. In this case, however, the annular working spacewould need to be placed ini communication 'withthe usual compressed gasfchamber, for the 'cylinder space normally contains liquid. Theinvention is, moreover, applicabile to the telescopic struts used forthe undercarria-ges of aircraft, although it is primarily intended 'foruse in suspension devices of motor vehicles.

What I claim isi: Y

-1. A telescopic 'suspension device comprising a cylinder closed 'at oneend, a packing gland at theother end, a piston slidable in saidcylinder, a stem of reduced diameter extending axially from 'the vpiston'and `Iriassing sl'idablyl through said packing gland., lsaid cylinderthus having a cylinder Work-'ing space ybetween the piston andV theclosed end and an La'rfinular working space surrounding the stem betweenthe back of thepiston and the packing gland, compressed airsubstantially filling both of said werking spaces,

1 adamping valve dev-ice disposed within the pisduri-ng normalreciprocati'on of the piston, anA

annular slnubbi-ng valve member slidably fittingwithin the cylinder borebetween the piston 'and the packing gland, vandY lannularseating 'meanson the piston, between the damping valve ports and' the packinggland,adapted to `engage the sn-ubbing valve mein-ber `when the suspension"devi'ce becomes extended beyond a predetermined length, the snubbingvalve member then completely seal-ing the annular working space so thatthe compressed gas disposed therein is trapped and is rapidly compressedby continued extending movement of the suspension device.

2. A telescopic suspension device comprising a cylinder closed at oneend, a packing gland at the other end, a piston slidable in saidcylinder, a stem of reduced diameter extending axially from the pistonand passing slidably through said packing gland, said cylinder thushaving a cylinder working space between the DiStOn and the closed end,and an annular working space surrounding the stem between the back ofthe piston `and the packing gland, compressed gas substantially fillingboth of said working spaces, a damping valve device disposed Within thepiston, damping valve ports in the piston, said damping valve providingrestricted connection between the cylinder working space and the annularworkmg space by Way of said damping valve ports during normalreciprocation of the piston, an annular snubbing valve member slidablyfitting Within the cylinder bore between the piston and the packinggland, a support member within the annular working chamber, whichsupport is axially compressible, and annular seating means on thepiston, between the damping valve ports and the packing gland, adaptedto engage the snubbing valve member when the suspension device becomesextended beyond a predetermined length, the snubbing valve member thencompletely sealing the annular working space so that the compressed gasdisposed therein is trapped and is rapidly compressed by continuedextending movement of the suspension device, the support member normallyholding the snubbing valve member in a prescribed position determiningthe commencement of the snubbing action.

3. A telescopic suspension device as claimed in claim 2, wherein thesupport member comprises a coiled compression spring which is normallyfree to assume its natural full axial length.

4. A ytelescopic suspension device comprising a cylinder closed at oneend, a packing gland at the other end, a piston slidable in saidcylinder, a stem of reduced diameter extending axially from the pistonand passing slidably through said packing gland, said cylinder thushaving a cylinder working space between the piston and the closed end,and an annular working space surrounding the stem between the back ofthe piston and the packing gland, compressed gas substantially fillingboth of said working spaces, a damping valve device disposed within thepiston, damping valve ports in the piston leading into a narrow annularclearance space between the piston and the cylinder, said damping valveproviding restricted connection between the cylinder working space andthe annular working space by way of said damping valve ports and annularclearance space during normal reciprocation of the piston, an annularsnubbing valve member slidably tting within the cylinder bore betweenthe piston and the packing gland, and annular seating means on thepiston, between the damping valve ports and the packing gland, adaptedto engage the snubbing valve member when the suspension device becomesextended beyond a predetermined length, the snubbing valve member thenbridging the said clearance space and completely sealing the annularworking space so that the compressed gas disposed therein is trapped andis rapidly compressed by continued extending movement of the suspensiondevice.

5. A telescopic suspension device as claimed in claim 1, wherein theannular snubbing valve member comprises a ring of soft resilientmaterial slidably engaging the cylinder, and a rigid metal washerengaging that side of the ring nearest the packing gland, the oppositeside of said resilient ring being engageable with the piston to seal theannular working space from the damping valve and cylinder working space.

6. A telescopic suspension device as claimed in claim 1, wherein aplurality of resilient tongues disposed adjacent the seating means onthe piston act to urge the snubbing valve member out of engagement withsaid seating means during shortening of the suspension device.

7. A telescopic suspension device as claimed in claim 1, wherein theannular snubbing valve member comprises a ring of soft resilientmaterial having a triangular shape in cross section, and a rigid metalWasher engaging that side of the ring nearest the packing gland, theopposite side of said ring being of hollow frusto-conical shape, theseating means on the piston being frustoconical to correspond, so thatas the piston reaches the snubbing valve member during extension of thedevice, said seating means spreads the resilient ring outwards intosealing engagement with the cylinder.

PETER WARBORN THORNHILL.

REFERENCES CITED The following references are of record in the le o thispatent:

UNITED STATES PATENTS Number Name Date 1,886,712 Messier Nov. 8, 19322,089,657 Mercier Aug. 10, 1937 2,098,398 Mercier Nov. 9, 1937 2,275,462Parilla Mar. 10, 1942 2,372,137 Thornhill Mar. 20, 1945 FOREIGN PATENTSNumber Country Date 49,470 France Jan. 17, 1939 408,592 Great BritainApr. 5, 1934

